1. Field of the Invention
The present invention relates to an apparatus for and a method of measuring a workpiece on a machine tool with a measuring head which is detachably mounted on a main spindle of the machine tool.
2. Description of the Related Art
In the field of machine tools such as machining centers, there has already been proposed a technology for measuring the configuration of a surface of a machined workpiece mounted on a machine tool without the need for removal of the machined workpiece from the machine tool. For example, PC(WO) 2007-518579 discloses a workpiece inspection system for use with machine tools.
The disclosed workpiece inspection system includes a probe, which corresponds to a measuring head according to the present invention, mounted on a main spindle of a machine tool. When the feeler of the probe contacts a workpiece on the machine tool, the workpiece inspection system measures the workpiece with the probe and acquires measured data from the probe. At the same time, an existing NC (Numerical Control) apparatus combined with the machine tool acquires positional data of the probe. The workpiece inspection system then inspects the workpiece based on a combination of the measured data and the positional data.
The workpiece inspection system disclosed in PC(WO)2007-518579 makes it necessary to modify or change the existing NC apparatus for adding new functions thereto. The probe outputs a much larger number of measured data than positional data acquired by the NC apparatus. The disclosed workpiece inspection system selects a necessary number of measured data from the large number of measured data output by the probe. As a result, the measured data tend to be brought out of synchronism with the positional data, making the workpiece inspection system difficult to produce highly accurate inspection results.
Since the number of generated measured data is large, the overall data to be handled are enormous. As a consequence, the disclosed workpiece inspection system requires an interface having a large processing capability for transmitting the measured data and a CPU having a large processing capability for processing the measured data. The workpiece inspection system also needs a memory having a large storage capacity for storing the measured data.
The disclosed workpiece inspection system operates to acquire measured data while the feeler of the probe is being held in contact with the workpiece. Therefore, it is difficult to scan the workpiece with the probe safely at a high speed in a vibration-free or low-vibration environment. It is also difficult to measure the workpiece over a wide surface range thereof within a short period of time.